1. Field of the Invention
The system for clamping and driving a work piece according to the invention relates, more precisely, to a work piece pre-positioned, in particular, on a mandrel or expandable centring means, the said system not affecting the initial position of the work piece in relation to its support.
2. Description of the Related Art
A number of work piece clamping devices are known, for example chucks for radial and axial clamping, but without compensated clamping, or again, chucks with one or more concentric or diameter compensated jaws, for radial clamping, with or without axial clamping, with modifiable distribution between radial clamping and axial clamping with compensation of the said clamping and distribution of the clamping force practically equal on each jaw, as disclosed in document FR-A 2373 351.
More recently, these systems have been modified by producing a clamping chuck permitting more accurate radial guiding of the jaw holders in the body of the chuck, which also ensures that they are free to pivot axially with a view to optimum positioning of the jaws in contact with the work piece for clamping. For this purpose, each jaw holder is equipped with a member guided along a groove provided in the chuck, the said guide member being free solely to pivot axially in relation to the jaw holder, as disclosed in document U.S. Pat. No. 5,605,343 in the name of the Applicant.
However, there are cases in which the said devices cannot be entirely suitable, such as, for example, for a work piece pre-positioned on an expandable centring means and that one would like to be able to clamp without thereby changing the said pre-positioning. It is sometimes advisable, in fact, in the case, for example of an internally threaded hollow work piece, the thread of which bears against a centring support, not to cause the said work piece, when it is clamped, to be displaced in relation to the support, which could be detrimental to the said work piece, for example by blunting or damaging its thread.